“Some part of her body was always touching him—at one point hip to hip,” says the partygoer. “She was also giving him the filthiest looks, whispering in his ear, and turning everything he said into an innuendo.”

The pair are said to have exchanged numbers that night, with Lohan calling four times a day and sending suggestive text messages, resulting in

nonstop ribbing from Crawford’s Gossip Girl castmates.

“Sam will go mad when she finds out,” a source reveals. “Chace has been advised to give the couple a very wide berth.”

Good call; there’s no telling what Ronson might be capable of if she gets herself all hopped up.

LiLo might want to watch her back too; there may be stiff competition for Crawford’s affections.